The present invention relates to a mass spectrometer for analyzing ultra trace element using plasma ion source and more particularly to the mass spectrometer in which position of a plasma generating portion is optimized so as to improve sensitivity of the mass spectrometer.
In the general mass spectrometer for analyzing ultra trace element, the most popular one is a ICP-mass spectrometry and an example of such device is cited in a publication named "Application of Inductively Coupled Plasma Mass Spectrometry" edited by A. R. Date et al and published by Blackies and Son Ltd. in U.S.A. on 1989. In this publication, it is shown that the mass spectrometer has attained a detecting limitation of PPT level such as 1/10 g/g and has the highest sensitivity than that of any other instrument for measuring the trace element.
In the ICP-mass spectrometry as stated above, nebulized sample is dissociated into ions in air by heat (about 5000-6000 C.) of the ICP plasma and these dissociated ions are transmitted into a vacuum chamber trough an interface so as to be analyzed respective elements by elements with the mass spectrometer.
The every elements are detected by a detector which outputs pulse signals corresponding to the every elements and the pulse signal is amplified and counted by a pulse counter.
The such conventional ICP-mass spectrometry has the highest sensitivity as stated above, but it is difficult to adjust the mass spectrometer so as to detect data in the highest efficiency because the detected data varies depending on various parameter such as voltage of an ion lens, the detecting sensitivity in mass analyzing portion etc. and it takes much times to adjust the mass spectrometer so as to detect data in the highest efficiency.